This paper is based on the premise that relatively little is known about how to improve validity in qualitative research and less is known about how to estimate validity in studies conducted by others. The purpose of the study was to describe the conceptualization of validity in qualitative inquiry to determine how it was used by the author of a research study, and to present a revised conceptualization of validity and suggestions for improving and estimating it. Validity is defined as the adequacy of a research report or other datum as a representation of some phenomenon for a particular purpose. Suggestions for improving validity are given for the stages of research design, data collection, data analysis, and reporting. Estimating validity requires making informed judgments about the adequacy of a research report for a particular purpose and includes considerations of correspondence between the representation and studied phenomenon; appropriateness of focus, scope, and intensity; and understandability. The assessment of validity in qualitative inquiry appears to be more judgmental, more relative, and less precise and certain than in quantitative inquiry. (PN)